Various types of chromatography, so-called preparatory chromatography, are employed as a means for isolating a pure substance from a mixture or separating a mixture. Of the chromatography, widely utilized is liquid chromatography, particularly high-performance liquid chromatography (HPLC).
Pure substances are different in the molecular size, molecular shape, electric charge, viscosity, mobility, and polarity, and are greatly different in the extent of the interaction with a packed material of chromatography, resulting in difference of migration rates in the chromatography. By utilizing the difference of the migration rate, a mixture can be separated into its components. From the viewpoint of transfer of a pure substance by the principle of the separation, the chromatography apparatus including the HLPC is regarded as a mass transfer device.
The HLPC employs widely a capillary column packed with a particulate packing material. The particulate packing material includes particulate porous silica gel, surface-modified particulate silica gel, and particulate polymer gel, having a particle size of about 5 to about 10 μm.
On the other hand, with development of microfabrication techniques in recent years, the systems are attracting attention which comprise a fine flow channel, microfluidic devices such as a pump, and a valve, and a sensor integrated on a substrate like glass or silicon, and which conduct chemical analysis on the substrate. Such a system is called a microanalysis system, a μ-TAS (Micro Total Analysis System), or a Lab on a Chip. The miniaturization of the chemical analysis system enables decrease of a noneffective space volume and remarkable decrease of the sample size as well as shortening of the analysis time and decrease of power consumption of the entire system. Further, the miniaturization is promising for lowering the price of the system. Furthermore, the U-TAS is promising in medical services such as home medial care and bed-side monitoring, and biological chemical techniques such as genomics and proteomics analysis.
HLPC is promising for increasing the performance and lowering the cost by miniaturizing the system to form a fine flow path packed with a packing material. However, a conventional particulate packing material cannot readily be packed uniformly into a fine flow channel owing to the shape and size of the particles.
Japanese Patent Application Laid-Open Nos. 9-329590 and 11-133014 disclose columns employing a silica gel of a double pore structure without using a particulate packing material. The columns are prepared by treating a silica gel chemically and thermally in a tubular mold of inside diameter of 10 mm, and after the molding, the surrounding surface is solidified by an epoxy resin in a form of a rod column. However, the column prepared by the above method has a diameter of 10 mm and a length of about 83 mm. Therefore, the column is not useful for μ-TAS.
Japanese Patent Application Laid-Open No. 2000-218629 discloses a process for injection-molding a μ-TAS chip having a groove as a flow channel. However, this μ-TAS chip is not packed with a packing material, so that it is not useful for HPLC.
U.S. Pat. No. 6,344,120 discloses a process for forming a porous silica structure in a flow channel by forming a microscopic channel path on a surface of a plate, introducing a solution in a sol state into the flow channel, and allowing the solution to gel in the flow channel.